Reading data from a vector of class of vector - c ++ - c++

Question

I have a class which made of a ints and strings, but I also have a vector inside that class. I have to read the records from a file and then after parsing each line, put the info in my vector of class. I have to get the basic package information like ID and name and then add the services which are offered with that package, so I can have 10 records that are from one package but they are different in type of services. For now I am trying to work out putting the data in each package and access the data from each element, but when I am trying to get the data from the vector inside the class, my compiled file crashes. It also prints out the 1233 and foo, but not the test. Any ideas why is that?
int main()
{
vector<package> packs;
package pack;
pack.ID = 1233;
pack.name = "foo";
packs.push_back(pack);
pack.putData("test",12);
cout << packs[0].name << endl;
cout << packs[0].ID << endl;
cout << packs[0].bservice[0].serviceID << endl; //[b]Crashes in this line[/b]
return 0;
}
Defined class is:
class package
{
public:
class aservice
{
public:
int serviceID;
string othername;
};
int ID;
string name;
vector<aservice> bservice;
void putData(string name1, int serviceID1)
{
aservice obj;
obj.serviceID = serviceID1;
obj.othername = name1;
bservice.push_back(obj);
}
};

Answer 1

Here you make a copy of pack when you push_back into the vector:
packs.push_back(pack);
And here you access pack, not the copy stored in your vector
pack.putData("test",12);
So the bservice vector you are trying to access is actually empty, which is why your code crashes when you try to access it here:
cout << patients[0].bservice[0].serviceID << endl; // patients[0].bservice is empty!!!
You can avoid this by pushing back after the call to putData:
vector<package> packs;
package pack;
pack.ID = 1233;
pack.name = "foo";
pack.putData("test",12);
packs.push_back(pack);
You can also avoid it by not trying to access a vector without first checking whether it is empty.
Ideally you should strive to design classes than can be constructed into a useful state, as opposed to default constructing them and adding data step by step via setters. This is particularly important if the data are inter-related and the class must maintain invariants.

Answer 2

packs.push_back(pack);
Is going to push a copy of pack into your vector. You will therefore have two specific instances : if you call putData on one of those, the other one will not be modified itself !
Therefore, when writing
patients[0].bservice[0]
your application crashes because you did not putData inside patients[0], only inside pack - which is, once again, a different object.
You should modify your vector so it stores pointers to package's, and push the adress of pack inside.

Answer 3

pack.push_back(pack);
Assuming the first pack is actually packs, this pushes a copy of pack onto the vector.
pack.putData("test",12);
This modifies the local variable pack, but not the copy you pushed onto the vector. That still contains an empty bservice vector.
cout << patients[0].bservice[0].serviceID << endl;
Assuming that patients is actually packs, this erroneously attempts to read from the empty bservice vector.
You either want to call putData before packs.push_back(pack), or call it on packs.back() rather than the local pack.

Answer 4

Try this:
#include <vector>
#include <iostream>
using namespace std;
class package
{
public:
package(int inID, const string& inName ) : ID(inID), name(inName)
{
}
void putData(string name1, int serviceID1)
{
aservice obj;
obj.serviceID = serviceID1;
obj.othername = name1;
bservice.push_back(obj);
}
void Print() const
{
cout << ID << endl;
cout << name << endl;
vector<aservice>::const_iterator iter;
iter = bservice.begin();
for (; iter != bservice.end(); ++iter)
{
cout << iter->serviceID << " " << iter->othername << endl;
}
}
private:
class aservice
{
public:
aservice() {};
int serviceID;
string othername;
};
int ID;
string name;
vector<aservice> bservice;
};
typedef vector<package> PackContainer;
typedef vector<package>::iterator PackContainerIterator;
typedef vector<package>::const_iterator PackContainerConstIterator;
void PrintAll(const PackContainer& packs)
{
PackContainerConstIterator iter = packs.begin();
for (; iter != packs.end(); ++iter)
{
iter->Print();
}
}
int main()
{
PackContainer packs;
package pack( 1233, "foo");
pack.putData("test",12);
packs.push_back(pack);
PrintAll(packs);
return 0;
}